An electrode is a conductor, usually metal, immersed in an electrolyte solution (i.e., electronic conductor in contact with an electrolytic conductor) that serves either as a source (the cathode) or sink (the anode) of electrons. The application of an electromagnetic force, e.m.f., between two such electrodes in an electrolyte solution will give rise to electrochemical reactions on the surface of both electrodes. The nature of the electrode material dictates the electrochemical reactions that will occur.
Mercury is widely used as an electrode in the practice of electroanalytical chemistry. The dropping mercury electrode, DME, is the essential component of all polarographic experiments. Usually, the DME is formed by glass capillary tubing connected to a standpipe of plastic or glass attached to a mercury reservoir. If the level of mercury in the standpipe is sufficiently high with respect to the tip of the capillary, mercury flows from the capillary at a steady rate, small drops form at the end, and the drops fall at a regular interval. Electrolysis is carried out on the surface of the mercury drops.
One of the most important advantages of the DME is continuous renewal of the electrode surface. As the old drop falls away, a new drop is formed providing a fresh, clean surface for electrolysis reactions. A major disadvantage of the DME is its small size makes it inapplicable for large scale electrochemical processes.
Examples of large scale electrochemical processes are electrowinning, electrorefining and the electrochemical generation of hydrogen. Anodic processes include inorganic and organic systhesis and the electrochemical generation of oxygen and chlorine. Electrodes used in these processes are generally metal.
In conventional large-scale electrolysis, the electrolysis products typically are deposited on the surface of the electrodes. For gaseous and liquid products, the isolation of these products from the cathode and anode is easily accomplished. Solid products, on the other hand, require additional chemical methods to achieve isolation. In many applications, this deposition of the solid product at the working electrode is the desired result, as is the case in electroplating. However, in other applications, it would be advantageous to have a system in which the solid product is easily isolated, for example, in the processing of metals and metal alloys. Also, in conventional electrolysis, side reactions may occur resulting in the corrosion of the electrodes. Thus, an electrode surface which is renewable would be beneficial to minimize corrosion.
The present invention addresses the problems associated with electrolysis described above, namely, easy recovery of electrolysis product and renewability of the electrode surface. A description of the present invention as well as the objectives of the invention are discussed below.